1. Field of the Invention
The present invention relates to a liquid material-vaporizing and supplying apparatus, for example a liquid material-vaporizing and supplying apparatus provided with a vaporizer capable of quantitatively vaporizing liquid materials, such as tetraethoxysilane, in the production of semiconductors for supplying various kinds of use, such as a chamber of the apparatus for producing semiconductors, with vaporized gases generated in said vaporizer.
2. Description of the Prior Art
A liquid material-vaporizing and supplying apparatus, in which a liquid material tank 103 as a vaporizer housing a liquid material LM therein and heated by a heater 102 is provided in a thermostatic oven 101, a gas flow rate controller 105 integrally comprising a control valve and a flow meter through a stop valve 104 is connected with said liquid material tank 103, and a gas flow meter 107 is connected with an upstream side of said stop valve 104 through a stop valve 106, whereby heating said liquid material LM by said heater 102 under the condition that said stop valve 106 is closed to control a flow rate of a gas G generated at that time by means of said gas flow rate controller 105, as shown in FIG. 15, has been known as one example of the conventional liquid material-vaporizing and supplying apparatus.
In addition, a liquid material-vaporizing and supplying apparatus, in which a liquid material LM is introduced into a vaporizer 112 heated by a heater 111 through a liquid flow rate controller 113 and a stop valve 114 and a carrier gas CG is introduced into said vaporizer 112 through a gas flow rate controller 115 and a stop valve 116 to measure a flow rate of a gas G generated in the vaporizer 112 at that time by means of a gas flow meter 118 provided in a heating pipe 117 on the downstream side of the vaporizer 112, as shown in FIG. 16, has been known as another example of the conventional liquid material-vaporizing and supplying apparatus.
However, in said liquid material-vaporizing and supplying apparatus shown in FIG. 15, disadvantages have occurred in that it is necessary to heat the liquid material tank 103 by the heater 102 and the liquid material LM is always influenced by heat, so that the liquid material LM is thermally decomposed or changed in composition (changed in quality) according to circumstances and impurities are dissolved out from the liquid material tank 103 to mix in the liquid material LM. And, disadvantages have occurred in that the gas flow rate is directly controlled, so that a time from a start of gas generation to a stabilization of gas flow rate is greatly dependent upon a performance of the gas flow rate controller 105 and the gas flow rate controller 105 of high performace so much as that must be used and thus the cost is increased. Moreover, problems have occurred in that a pressure loss in a control valve of the gas flow rate controller 105 comes into question and thus it is necessary to use a control valve having a high CV value in order to suppress said pressure loss to a reduced value, but, as a result, the gas flow rate controller 105 is large-sized and the cost is increased.
Furthermore, in said liquid material-vaporizing and supplying apparatus shown in FIG. 16, a high-temperature portion comprises merely the vaporizer 112 and the liquid material LM-supplying system can be composed under a room-temperature condition, so that a problem that the liquid material LM stored in the liquid material tank is thermally decomposed or changed in composition can be avoided but the gas flow rate is apt to be influenced in stability, reproducibility and the like by the performance of the liquid flow rate controller 113 and the performance of the vaporizer 112 or the temperature condition, so that, in the case where the gas flow rate is monitored, it is necessary to separately provide the liquid material-vaporizing and supplying apparatus with a high-temperature gas flow meter 118, whereby passing the carrier gas CG and the vaporized gas G.
By the way, in both of the above described liquid material-vaporizing and supplying apparatus, the quantity of vaporized gas G generated is measured by the gas flow rate controller 105 or the gas flow meter 118, so that it is necessary to periodically check the gas flow rate controller 105 or the gas flow meter 118 in performance.
For example, in the liquid material-vaporizing and supplying apparatus shown in FIG. 15, an inert gas is introduced as a monitor gas MG under the condition that the stop valve 104 is closed and the stop valve 106 is opened to compare a flow rate value detected by the gas flow rate controller 105 at that time with a flow rate value detected by the gas flow meter 107 provided on the upstream side of the gas flow rate controller 105.
In addition, in the liquid material-vaporizing and supplying apparatus shown in FIG. 16, the liquid material LM is introduced with controlling by the liquid flow rate controller 113 to monitor the gas G generated at that time by the gas flow rate controller 118 provided on the downstream side of the vaporizer 112.
However, in the liquid material-vaporizing and supplying apparatus shown in FIG. 15, a disadvantage has occurred in that the vaporization of liquid material LM must be stopped in order to control the flow rate and thus the continuous control cannot be achieved.
Moreover, in the liquid material-vaporizing and supplying apparatus shown in FIG. 16, although such a disadvantage as in the liquid material-vaporizing and supplying apparatus shown in FIG. 15 does not occur, not only the carrier gas CG is required but also the generated gas G is mixed with the carrier gas CG, in particular in the case where a thermal mass flow meter is used as the gas flow meter 118, the mixture gas of the carrier gas CG and the generated gas G is different in density and specific heat in dependence upon their mixed condition, so that the conversion must be conducted by the use of various factors to determine the quantity of generated gas G.